Synthesis, characterization, and reactivity of zinc carboxylate complexes of 2,3-pyridine dicarboxylic acid and (3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)acetic acid

Ethylenediammonium tris-2,3-pyridine dicarboxylato zinc(II) trihydrate (enH2)2[ZnL3]·2H2O (1) (where H2L = 2,3-pyridine dicarboxylic acid, en = ethylenediamine) and a mixed metal coordination polymer with composition [Na2ZnL′3(OAc)(H2O)3]n (2) {where L′ = anion of (3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)acetic acid} are synthesized and characterized. The complex 1 is mono nuclear complex with three coordinating carboxylate anion along with nitrogen chelating zinc ion and there is three uncoordinated carboxylate group one each from three ligand molecules making a complex anion of zinc(II). The zinc(II) ion are in distorted octahedral coordination geometry. In this complex diprotonated ethylenediamines serve as cations. The complex 2 has a polymeric structure with one acetate and three carboxylate of L′ binding to zinc ion provides a tetrahedral environment and these ligands further hold dinuclear units of tri-aquated sodium ions; each dinuclear sodium units are bridged by one water molecule make the coordination polymer. The catalytic ability of these two complexes 1 and 2 towards carbon–carbon bond formation reaction between 3,4-dimethoxy benzaldehyde and acetone are studied. Both the complexes as well as sodium salt of L′ are found to be catalyst for such reactions.

Two complexes namely ethylenediammonium tris-2,3-pyridine dicarboxylato zinc(II) and coordination polymer of sodium and zinc having (3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)acetate and acetate bridge are synthesized and characterized; these complexes act as catalyst for aldol reactions.Figure optionsDownload as PowerPoint slide